Theoretically, multiple devices connected to Wi-Fi doesn’t slow down the internet speed. But in practice, more the number of devices are connected to the internet, the bandwidth is being shared thus affecting the speed. Here, if you are closer to the access point, then obviously your bandwidth should be higher than someone who is far away.
Internet speed depends on the type of usage also. This means that browsing web pages or sending email consumes only a small portion of bandwidth even if a number of users are performing this activity at the same time. On the other hand, streaming live videos and downloading large files consumes a sizeable bandwidth. If many users or most of the users are streaming HD videos or downloading large files on a consistent basis, then you will experience a considerable impact on bandwidth. Similarly, if a user utilizes significant bandwidth by sending large files, other users in the network will find it difficult to submit download requests.
In the same way, internet bandwidth can be impacted when multiple devices are connected to the same internet link and result in reduced performance as each device would be getting a smaller bandwidth share. Even a high-speed internet will deliver poor results if it is hampered by the local network inside your premises. So, it is worth keeping in mind the fact that the activities performed by the internet and the devices or users connected to it can have a large impact on the internet traffic and available bandwidth. The presence of a number of Wi-Fi devices in close proximity also degrades performance as these routers generate wireless signal interference which results in frequent re-broadcasting of messages that fail to reach the destination.
The majority of the users don’t know how many users can their router support. You can Google the model number and will be able to find it. There are routers which give administrative privileges to control the number of clients that can be simultaneously connected to the internet.
In the home network, all devices usually share a single internet connection. The performance starts to degrade the moment more users or devices are added to the network. This problem can be resolved by installing a second router to distribute the network load. By doing this, any number of devices can be supported. However, this will make the network complex and difficult to manage.